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Issue
EPL
Volume 86, Number 5, June 2009
Article Number 56002
Number of page(s) 6
Section Condensed Matter: Structural, Mechanical and Thermal Properties
DOI http://dx.doi.org/10.1209/0295-5075/86/56002
Published online 11 June 2009
EPL, 86 (2009) 56002
DOI: 10.1209/0295-5075/86/56002

Imbibition in layered systems of packed beads

M. Reyssat1, L. Y. Sangne1, 2, E. A. van Nierop1 and H. A. Stone1

1   School of Engineering and Applied Sciences, Harvard University - Cambridge, MA, 02138, USA
2   Western New England College - Springfield, MA, 01119, USA

mreyssat@seas.harvard.edu
mathilde.reyssat@espci.fr

received 20 February 2009; accepted in final form 11 May 2009; published June 2009
published online 11 June 2009

Abstract
We study imbibition of a wetting fluid into layers of packed beads and examine how variations of permeability in the flow direction affect the dynamics of imbibition. In the case of systems made of two distinct layers, we show that the imbibition dynamics exhibit three regimes including diffusive-like imbibition as well as an unusual constant speed imbibition, which can be fine-tuned by adjusting the bead diameters and the length of the initial layer. We also perform experiments with gradients of permeability by ordering layers of beads of increasing (or decreasing) sizes in a tube. A continuum description is used to explain the results from the discrete experimental systems. In all cases, analytical models based on Darcy's equation show excellent agreement with the experiments.

PACS
68.08.Bc - Wetting.
81.05.Rm - Porous materials; granular materials.
68.03.Cd - Surface tension and related phenomena.

© EPLA 2009